Telephone system



H. STEIDLE.

TELEPHONE SYSTEM. I

APPLICATION FILED OCT. 5, I914- RENEWED OCT. 29. 1919.

1,332,275. v Patented Mar. 2,1920.

2 SHEETS-SHEET 1.

H. STEIDLE.

TELEPHONE SYSTEM.

APPLICATION FILED OCT. 5. 1914. RENEWED OCT. 29.

Patented Mar. 2, 1920.

2 SHEETS-SHEET 2 llti HANS STEIJDLE, F MUNICH, GERMANY, ASSIGNOR, 1'0 SIEMENS & HALSKE, A. Gr., 0F SIEMENSSTADT, NEAR BERLIN, GERMANY, A CORPORATION OF GERMANY.

TELEPHONE SYSTEM.

Specification of Letters Patent.

Application filed October 5, 1914:, Serial No. 865,152. Renewed October 29, 1919. Serial No. 334,377.

To all whom it may concern:

Be it known that l, Hens S'rnmmi, a German citizen, and resident of Munich, Bavaria, Germany, have invented certain new and useful Improvements in Telephone Systoms, of which the following is a specification.

My invention relates to a telephone system with automatic or semi-automatic operation and branch-exchanges and has for its ob'ect primarily to provide an especial kind of linesclecting for such branch-exchanges.

in telephone systems as ordinarily con,- structed or proposed for automatic or semiautomatic service the so-called connectors have mostly been constructed for 100 or more subscriber connections, so that hundredsgroups will be obtained as smallest groups when subdividing the outside plant. The other systems which had been proposed relate entirely to an unlimited service, that is to say, to arrangements whereby the subscriber when calling will find at any time a free connecting line. It is known that the larger the groups are the smaller may be the percentage of incoming trunks.

Also systems of this kind have been constructed for a limited service which are ordinarily called branch-exchange systems; in this case for instance five subscribers are connected to a single trunk-line or ten subscriber lines are connected to two trunk lines. in the ordinary practice groups comprising each ten subscriber lines and two trunk-lines are most frequently used.

Such branch-exchanges are located in apartment houses or the like, where the traliic is small. The service rendered in such branch exchanges shall be restricted to some extent, that is to say, the serviceis' to be sold at a lower rate than the unrestricted service. In the ordinary unrestricted service the subscriber will always get a free trunk line to any group of the system whenever he calls. Whereas in the restricted service he will not be entitled to a tree trunk line at every moment, he calls.

In the well known automatic telephone systems for unrestricted service it is common practice to combine the subscr1bers lines into groups of 100 to 500 lines and to run about to 410 trunk lines to these groups. These trunk lines start at so-called second or third selectors which are arranged to be set first by number impulses on the contacts of the desired group and then to 1 hunt for a tree trunk line.

Qne object of my invention is to simplify the mechanism to be provided for the branch exchanges with restricted service.

Another object of my invention is to combine this simplified system with the well known system for unrestricted service.

In the drawings 1 have shown the well known Strowger type of switches as applied to the unrestricted system; it being, however, understood that the system is not limited to such type of switches.

Figure 1 diagrammatically shows the combination of the two types of exchanges re- J'Eerred to in a so-called four digit system. Figs. 2 and 2* show a diagram in detail for establishing a talking connection between a subscriber of a main exchange with a subscriber of a branch exchan e.

Referring to Fig. 1, i N designate subscribers stations which pay for unrestricted service. The method for establishing a connection between the stations N,, N, is well known, the first selector GW being set by the thousand digit, the second selector GVV by the hundred digit, and the connector LW by the ten and unit digits.

N designates a subscriber of a branch exchange. Assume the station N be numbered 525 and connected to the branch exchange GS numbered from 520 to 529. Nine other branch exchanges numbered 500 to 509, 510 and 519, and so on, may be provided in neighboring houses. Two trunk lines connect each branch exchange with the main exchange.

It now the subscriber N, Wishes to call the subscriber 1T3 (having the number 525) the setting of the first and second selectors GVV GW is accomplished in the well known manner. Each trunk line issuing from the fifth row of bank contacts of the second selector GW leads to a special selector S of which only one is shown in Fig. 1. The selector S has as many sets of wipers (6,, 7),) as there are trunk lines running to each branch exchange. In the example shown two sets of wipers are provided. The subscriber N, will set the selector S by number impulses on the second row of contacts. If the trunk line Z, leading to a switch L, of the branch exchange GS is engaged by another selector S the second set of wipers (6 will come inboperation. The sub-. scriber N, will now be connected-by the trunk line Z to the switch L of the branch exchange GS. {By a last set of number impulses the switch L, will be set on the desired number.

By this system the lines of the hundred subscribers (No. 500 to 599) may be made very short, and only 20 trunk lines are to be run to the main exchange, instead of carrying all hundred subscribers lines to said main exchange.

. In Fig. 2 I have shown in detail a diagram for establishing a connection between a subscribers station N, of a main exchange and a subscribers station N of a branch-exchange. In this case I have shown a system controlled by number impulses in which during the rotation of the dial to its normal position the b-line constantly connected to ground whereas the a-line is alternately connected to ground and disconnected therefrom.

The setting of the first and second selectors GW and 'GVV is accomplished in the well known manner, it being understood that the line relay B is kept energized as long as the calling subscriber N, keeps his receiver off the hook. Therefore, the contact b, is also kept closed and the following circuit established: ground, contact 7),, relay P,, wiper 12, relay C battery, ground. .This circuit keeps said relay C, also energized. The relay C, closes the contact 0,. If the selector GW has found a free selector S the testin relay P in the second groupselector GTV will respond, a circuit being established over ground contact 0, of relay C,, relay P wiper 15, contact 8,, relay C arm 0,, battery and ground. The relays P, and C, will be excited and P, will close a contact 10,, whereby the line will be guarded as known. The relay C closes the contact 0 in order to become independent from the contact 0,. This latter contact'o, is a seventh contact arm of the selector S,.while the contact arms 0,, 0,, 0 correspond to the set of brushes 1),, the contact arms 0,, 0 0,, to the set of brushes 6,, as shown in the arrangement according to Fig. 1.

If now the subscriber at the station N, again operates the dial, the relay X will be excited, the battery will be connected over the contact to the ZJ-strand and relay B, of the selector S will be excited, a circuit be' ing formed over ground, B,, contact 8 wipers 14, 1 1, b-strand, contact an, and battery, to ground. The excitation of this relay B, will be maintained until the dial returns to normal. During the return motion the flow of current will intermittently be interrupted over the calling a-strand and the armature of the relay A will fall ofi every time and close itscontact a At eacl closing of the contact a a current impulse will be established over ground, a 410 astrand, 10, 13, 8,, relay A,, and battery, to ground. The impulse relay A, now closes a circuit for the rotary magnet D of the selector S over ground, rotary magnet 1), 7a,, 41,, battery, ground. For each excitation of A, the seven contact arms 0,0, will be -moved one step. l

The selector S being set upon the desired branch exchange two lines Z, and Z may be available and now it must be tested which of these lines is free.

The relay 0, having also closed the contact 0 a circuit is established over ground, resistance, relay U contacts 70,, c and battery, to ground. The relay U becomes energized and closes the contact a, so that it wil remain excited, even it; the contact 70, will later be opened.

When operating the dial the relay B, has been excited as above described, and a circuit closed, ground, relay V, contact 5,, parallel over 70, and 2.5,, 0,, battery, ground. The relay V becomes excited and closes its contacts '0, and 0,, thereby preparing circuits for the test relays T and R. If after sending the impulses the relay B, becomes dee'nergized, the relay V being slow-acting will still remain excited for some time; and keep closed the following circuit: ground, 0 70,, b 1),, and test relay T, brush 0,, relay C battery, ground and ground, c 70,, b 0 relay R, brush 0,, and a further relay which corresponds to the relay G, (not shown).

If both lines Z and Z are free both relays T and. R will respond, relay T will open the contact and close contact t so that the relay T will become independent from the contact 0),. The relay R closes the'conta-ct 7 If the armature of the slow-acting relay V falls ofi and again opens the contacts a, and 71 the relay T will remain excited over contact A, the relay R, however, will become denergized since circuit is interrupted at contact t If therefore both lines Z, and Z are free they willboth be engaged for a moment, the test device of the first line however will switch off the test relay of the second line. If line Z, had been occu pied and Z free, the relay R would have become excited and bound itself over the contacts 7", and t If neither line Z, or Z, is free a busy signal will be given to the calling party, for if relay P does not respond its contact 1), will remain closed. The relay K, however, will become excited at any rate, as will be more fully described below. A circuit will therefore be established for the buzzer BS which indicates the occupied condition over BS, p, and induction coil J.

The series connection t and 7', replaces hurgting devices for selecting a free line Assume the test relay T to respond. It

will close a circuit: ground, P t 9,, a battery, ground. The relay P will take the function of the test relays T and R which must take place under all circumstances no matter whether T or R is responding.

When the armature of the slow-acting relay V falls off it closes a circuit: ground, battery, 0,, relay K, o, and ground. The relay K is energized and closes its contact 7a,, thereby becoming independent from contact o The relay K prevents the rotary magnet D of the selector S from responding to the next series of numeral impulses, by opening the contact By opening the contact in, the relay K also prevents an additional test ing by the relays T and R.

If new the subscriber at the station X sends the last series of impulses the relay B, will again be excited. The circuit changes in the selector S are as follows: When the back contact a, will be opened again a relay Q which had been short-circuited over the contacts a, and will be excited over ground, P 1%,, Q and battery. The relay Q opens the short-circuit at 9,.

During the last series of number impulses there are excited the relays A B K, U, V, P Q; and T. The purpose of the excitation of the relay V at this time is to open at contacts '0, and v the feeding bridge formed by the relay S. The excitation of the relay U in this moment has the purpose to keep open the contact at, in the circuit of the ringing relay L. When now at the calling station the a-strand 1s mterrupted the relay A, in the selector S will be excited in the well known manner and close a circuit over battery, protective resistance W contacts (1. b 3,, brush 0,, a-branch of the line Z 11,, impulse relay A ground, thereby energizing the relay A This will first excite a retarding relay F over the circuit ground, (r F, battery, ground, which closes a contact f When the impulse relay A, in the selector S releases its armature and the relay A, becomes deenergized, the switching magnet H of the selector L will be excited by a circuit over ground, f,, (1 H and battery. The brushes 0 0,, 0 make one step. Simultaneously with the magnet H a slow-acting relay G which is connected in parallel to H is excited. After completion of the last series of impulses the relay F will become denergized and close its contact By opening the contact f, the last current impulse for theretary magnet H will be completed. Since now the relay Gr being more sluggish will fall off some time after the opening of the contact 7, a test circuit for the relay P, will be temporarily closed over ground, 0 9, f P 0 e, resistance W and battery. If the called party N is free the relay P will be excited and close a contact 10,, render- -ing the circuit of the test relay independent from the contacts 7, and g, and guarding the engaged line. I

The relay P, also closes a contact 72 thus establishing a circuit over resistance W In the line leading to the station N a relay E is inserted which will be excited in case of outgoing as well as incoming calls. This relay will thereby open the contact e, so that a connector when testing will not find battery over the resistance "W It may be incidentally noted that the lines Z for incoming and m for outgoing calls may be coupled to each other or may be identical lines.

l f, the party l be free, the relay P, will close the contact 7),, and p, and switch off the impulse relay A, at 12 Therefore no bridge remains over the talking leads in the branch exchange.

The relay V in the selector S, as above mentioned, had been excited during the sending of the last impulses and the feeding bridge S had been switched off. Tf after completion of the last series of impulses the relay B, again falls off, first the contact 6, will be closed, thereby short-circuiting the relay U over 7), and (1 The relays U and V after some time will be deenergized. Relay U opens the contact a, and closes the contact 11 Contact 10 closes a circuit from groiuid, relay Tl, n 8,, c interrupter 1m, battery to ground. The relay L will periodically connect the line of the called station N, to a ringing current source over the contacts 7, and Z If the party N, answers, the feeding relay S will be excited over battery, S, o line of the called station N 1),, S, and battery.

The relay S will open the contact a, and thereby interrupt the ringing current. The relay S furthermore switches the calling line from the impulse relays A B to the contacts a, and 8,, whereby the repeating coil lle will be inserted into circuit It will be noted that during the periodical excitation of the relay L the signal free will be given to the calling party N over the contacts Z and p, and an induction coil upon the relay A,. By the excitation of the re lay S the contact 8, has been opened and .9, closed, causing the relay G to be deenergized while maintaining the holding current for the test relay P over the resist ance W The purpose of this switching operation is the following :Tf after completion of the conversation the called subscriber N, first restores his receiver the relay S will be deenergized and thereby the circuit of the ringing relay would again be closed at The party N would then believe that a new call had arrived. By opening the contact 0 at the first excitation of the relay S, however, the contact 0, will ill-W reJeatin coil We.

he opened, so that after deenergizing of the relay S the ringer circuit will not be closed again. The deeuergizing of the relay C will cause the relay S to perform all functions which had been given to the relay C; in particular the holding current. must be kept close for the test relay T over the contact a It the called subscriber first restores his receiver the relay C will be de energized. contact s, will also open, the relay T will he deenergized and open the con tact f,; the relay P, will drop its armature and close the contact 1),, whereby a circuit is closed over ground, I), 1a,, 1),, interrupter 1m, and battery. The brushes 0 to o, Wlll rotate until the brush 0 when coming normal releases the relay K, so that the contact A; will be opened and the selector S arrested. By the opening of the contact a, the circuit of the holding current for the relay C, in the connector L is interrupted and a contact c, closed, thus establishing a circuit over ground, interrupter 1m c brush 0,. H and battery. This circuit W'lll remain closed until the brush 0, gets into its normal position.

After the relay S has become deenergized the relays A, and B, are again connected to the trunk line. During the conversation the calling line had been made electrically inoperative by means of a condenser in the These diversities between the switching of the battery over the contacts a, and s and the interruption of the contacts a, and can be. utilized for controlling supervising relays in the trunkline office F, as shown in Fig. 1, in such a manner that a signal will be given at the responding of the subscriber N and that another signal will be given after completion of the conversation by the subscriber N,. The selectors VW, GVV and GW on the side of the calling subscriber are released in the well known manner.

It the called subscriber N is busy the testing relay P, will not respond and the calling subscriber N, will receive busy signal, the circuit being established over a busy machine, contact 0 in the connector, brush 0, induction coil on the relay A If the calling subscriber N restores the receiver the circuit for the holding current for the relays '1 and C, will be interrupted in the well known manner. If under these circumstances the relay C, falls off it will open its contact 0, and since 8 is not closed the relay T will be deenergized and the releasing operations will take place as above described.

Having thus described my invention I claim as new and desire to secure by Letters Patent of the United States 1. In a telephone exchange system, subscribers stations, subscribers lines with unrestricted service, subscribers lines with restricted service, trunk lines, selectors and connectors to establish connections between said lines, some of said selectors being set by number impulses and by an automatic operation to find a free trunk line, some of said connectors to be used for unrestricted service being set by a plurality of series of number impulses, others of said selectors and connectors for restricted service and in number equal to the number of said series of number impulses being arranged in series-and set by a single series of number impulses, the connection with a free trunk line issuing from the last of said selectors being made by a series of relays.

2. In a telephone exchange system, subscribers stations, subscribers lines with unrestricted service, subscribers lines with restricted service, trunk lines, selectors and connectors to establish connections between said lines, some of said connectors used for unrestricted service being set by a plurality of series of number impulses, some of said selectors and connectors for restricted service being arranged in series and in number equal to the number of said series. of number impulses and each set by a single series of number impulses, the trunk lines connecting said selectors and connectors for restricted service being less numerous than the number of subscribers lines connected to said connectors for restricted service, said selectors for restricted service havin as many sets of wipers as there are trunk ines to be reached by the same number.

In a telephone exchange system subscribers station's, subscribers lines with unrestricted service, subscribers lines with re stricted service, trunk lines, selectors and connectors to establish connections between said lines, some of said connectors used for unrestricted service being set by a plurality of series of number impulses, some of said selectors and connectors for restricted service being arranged in series and in number equal to the number of said series'of number impulses and each set by a single series of number impulses, the trunk lines connecting said selectors and connectors for restricted service being less numerous than the number of subscribers lines connected to said connectors for restricted service, said selectors for restricted service having as many sets of wipers as there are trunk lines to be reached by the same number, and a test relay for each set of wipers.

4. In a telephone exchange system, subscribers stations, subscribers lines with unrestricted service', subscribers lines with restricted service, trunk lines, selectors and connectors to establish connections between said lines, some of said connectors used for unrestricted service being set by a plurality of series or number impulses, some of said selectors and connectors for restricted service being arranged in series and in number equal to the number of said series of number impulses and each set by a single series of number impulses, the trunk lines connecting said selectors and connectors for I arranged in a series, each relay controlling the circuit of the succeeding relay in said series.

5. In a telephone exchange system, subscribers stations, subscribers lines with unrestricted service, subscribers lines with restricted service, trunk lines, selectors and connectors to establish connections between said lines, some of said connectors used for unrestricted service being set by a plurality of series of number impulses, some of said selectors and connectors for restricted service being arranged in series and in number equal to the number of said series of number impulses, and being each set by a single series of number impulses, talking battery and ringing current for said subscribers lines with unrestricted service being furnished from said connectors for unrestricted'service, and talking battery and ringing current for said subscribers lines with restricted service being furnished from said selectors for restricted service.

6. In a telephoneexchange system, subscribers stations, subscribers lines with unrestricted service, subscribers lines with restricted service, trunk lines, selectors and connectors to establish connections between said lines, some of said connectors used for unrestricted service being set by a plurality of series of number impulses, some of said selectors and connectors for restricted service being arranged in series and in number equal to the number of said series of number impulses and being each set by a single series of number impulses, said connectors for unrestricted service and said selectors for restricted service being connected to the said selectors for establishing connections between said lines, the circuits of said selectors for restricted service being arranged as number impulse repeaters to repeat the impulses sent by a calling subscribed to said connectors for restricted service.

7 In a telephone exchange system, subscribers stations, subscribers lines with unrestricted service, subscribers lines with restricted service, trunk lines, selectors and connectors to establish connections between said lines, some of said connectors used for unrestricted service being set by a plurality of series or number impulses, some of said selectors and connectors for restricted service being arranged in series and in number equal tolthe: number of said series of number impulses and being each set by a single series of number impulses, a source of current for operating said connectors and said selectors, talking battery and ringing current for said subscribers lines with un'- restricted service being furnished from said connectors for unrestricted service,

talking battery and ringing current for said subscribers lines with restricted service being'furnished from said selectors for restricted service, all connections between the talking lines of said connectors for restricted service and said source of current being broken after setting said connectors upon the desired line. I

8. In a telephone exchange system, subscribers stations, subscribers lines with unrestricted service, subscribers lines with restricted service, trunk lines, selectors and connectors to establish connections between said lines, some of said connectors used for unrestricted service being set by a plurality of series of number impulses, some of said selectors and connectors for restricted serv- 1ce being arranged n series and in number equal to the number of said series of number impulses and being each set by a single series of number impulses, a source of current for operating said connectors and said selectors, talking battery and ringing current for said subscribers lines with unrestricted service being furnished from said connectors for unrestricted service, talking battery and ringing current for said subscribers lines with restricted service being furnished from said selectors for restricted service, all connections between the talking lines of said connectors for restricted service and said source of current being broken after setting said connectors upon the desired line, another line leading from said selectors to said connectors for restricted service, and circuits connectedby said other .line for re leasing said connectors for restricted service.

9. In a telephone exchange system, subscribers stations, subscribers lines with unrestricted service, subscribers lines with restricted service, trunk lines, selectors and connectors to establish connections between said lines, some of said connectors used for unrestricted service being set by a plurality of series of number impulses, some of said selectors and connectors for restricted service being arranged in series and in number equal to the number of said series of number impulses and being each set by a single series of number impulses, the trunk lines connecting said selectors and connectors for restricted service being less numerous than the number of subscribers lines connected to said connectors for restricted service, and circuits arranged in said selectors torrestricted servic f r giving a busy signal o I the calling subscriber when all of said trunk lines between said selectors and said connectors for restricted service are occupied.

10. In a telephone exchange system, subscribers stations, subscribers lines with unrestricted service, subscribers lines with restricted service, trunk lines, selectors and connectors to establish connections between said lines, some of said connectors used for unrestricted service being set by a plurality of series of number impulses, some of said selectors and connectors for restricted service being arranged in series and in number equal to the number of said series of number impulses and being each set by a single series of number impulses, the trunk lines connecting said selectors and connectors for restricted service being less numerous than the number of subscribers lines connected to said connectors for restricted service, and circuits arranged in said selectors for restricted service for giving a busy signal to the calling subscriber when all of said trunk lines between said selectors and said connectors for restricted service are occupied, and circuits in said connectors for restricted service for giving a busy signal to said calling subscriber when the desired subscribers line is occupied.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

HANS 'STEIDLE.

Witnesses:

N. RoEnER, V. GUGGENBERGER. 

